The green swordtail (Xiphophorus hellerii; Poeciliidae) is a popular ornamental freshwater fish species. Fourteen microsatellites were isolated from a green swordtail genomic library enriched for CA-repeats. Thirteen microsatellites were polymorphic in green swordtail; interestingly four of them were tetranucleotide-type. Cross-species amplification showed that 10 of the 14 microsatellites were polymorphic in guppy (Poecilia reticulata; Poeciliidae) as well. No significant directional difference of allele length was seen between the two species at any of the loci tested.